Seatbelt restraint systems for restraining occupants in vehicle seats play an important role in reducing injuries in vehicle crash situations. Seat belt restraint systems of the typical 3-point variety have a lap belt section and a shoulder belt section which are connected together at one end. A latch plate (or tongue) which is releasably fixed to a buckle allows the vehicle occupant to fasten and unfasten the belt system. When the buckle and the latch plate are fastened together, the seat belt restraint system restrains movement of the occupant during a collision.
OEM motor vehicle manufacturers often incorporate pretensioning devices as part of the belt restraint system, which tension the seat belt prior to or during a vehicle impact. By reducing slack in the belts, early coupling between the occupant, belt system, and vehicle structure is provided which can reduce occupant loading and excursion (displacement). One type of pretensioning device is called a pyrotechnic lap pretensioner (PLP). Various designs are known, including a type of PLP which uses a cable to connect a piston at one end to seatbelt webbing at the other end. When a collision occurs, a pyrotechnic charge is fired, producing gas which pressurizes a gas chamber within a tube, forcing the piston down the tube. Since the seatbelt webbing is connected to the piston via the cable, the seatbelt is pulled with travel of the piston, tightening the belt around the occupant.
In one design for a seatbelt system using a PLP, the PLP device is mounted to the vehicle structure, such as to a seat or floor pan, and includes a cable extending along the side of the seat occupant. In order to facilitate assembly of the seatbelt system during vehicle manufacturing, a buckle is used to fasten the PLP to the belt system. This buckle attached at the PLP may be a so-called “fixing” type which is intended to be engaged and disengaged during vehicle assembly and disassembly, and not as the primary means for fastening and unfastening the belt system by the seat occupant during use. For that purpose, a separate latching buckle is provided. Seat belt buckles, for aesthetic reasons and for protection of internal components, include covers typically formed of plastic which encase the internal mechanisms.
During a vehicle impact event in which the PLP is activated, extreme forces are placed on all seatbelt system components. It is important that loose parts are not created during the vehicle impact situation by the restraint system. Loose objects can become hazards to vehicle occupants, particularly when traveling at high velocities within the vehicle compartment. The covers used for encasing the buckle benefit by having features which prevent them from becoming detached during PLP activation.
The present invention is related to a design of holding covers for a buckle which aids in their retention during a PLP actuation. The features include forming the holding covers in a clam-shell-type construction with first and second housing halves. The housing halves snap-fit together and form a tongue passageway for receiving the tongue and have sections which circumscribe the passageway such that upon insertion of the tongue, the cover halves are interlocked together. The covers further have portions which wrap around a slot formed by the buckle for receiving the belt webbing. By wrapping the webbing around the slot such that the holding covers are inside the loop formed by the webbing, an additional retention feature is provided.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which the present invention relates from the subsequent description of the preferred embodiment and the appended claims, taken in conjunction with the accompanying drawings.